Definition/Description

Piriformis syndrome (PS) is a painful musculoskeletal condition, characterized by a combination of symptoms including buttock or hip pain.[1][2][3] In several articles, piriformis syndrome is defined as a peripheral neuritis of the branches of the sciatic nerve caused by an abnormal condition of the piriformis muscle (PM), such as an injured or irritated muscle.[4][3] There are more women diagnosed with Piriformis syndrome than men, with a female–to–male ratio of 6:1. This ratio can be explained by the wider quadriceps femoris muscle angle in the os coxae of women.[5][6][3] There are two types of piriformis syndrome. The first type is called “Primary piriformis syndrome.” It is caused by an anatomical variation, like a split piriformis muscle, a split sciatic nerve or an anomalous sciatic nerve path. The second type is called “Secondary piriformis syndrome.” It is the result of a precipitating cause, such as a macrotrauma, microtraumata, ischemic mass effect or local ischemia.[6][3]

Clinically Relevant Anatomy

The piriformis muscle (PM) originates from the pelvic surface of the sacral segments S2-S4 in the regions between and lateral to the anterior sacral foramina, the sacro-iliac joint (superior margin of the greater sciatic notch), the anterior sacroiliac ligament and occasionally the anterior surface of the sacro-tuberous ligament. It passes through the greater sciatic notch to insert onto the greater trochanter of the femur.

The PM is functionally involved with external rotation, abduction and partial extension of the hip.[7][8]

The sciatic nerve generally exits the pelvis below the belly of the muscle, however many congenital variations may exist.[8]

The relationships between the PM and sciatic nerve have been classified by Beaton and Anson using a six category classification system (Beaton and Anson, 1938). An anomalous relationship would be labelled between type ‘‘B’’ through type ‘‘F’’ since type ‘‘A’’ is considered to have a normal relationship between the PM and the sciatic nerve.[9]

Variations in the relationship of the sciatic nerve to the piriformis muscle shown on the diagram above: (A) the sciatic nerve exiting the greater sciatic foramen along the inferior surface of the piriformis muscle; the sciatic nerve splitting as it passes through the piriformis muscle with the tibial branch passing (B) inferiorly or (C) superiorly; (D) the entire sciatic nerve passing through the muscle belly; (E) the sciatic nerve exiting the greater sciatic foramen along the superior surface of the piriformis muscle. The nerve may also divide proximally, where the nerve or a division of the nerve may pass through the belly of the muscle, through its tendons or between the part of a congenitally bifid muscle.[3]

Epidemiology /Etiology

According to Boyajian- O’ Neill L.A. et al., who has a level of evidence of 2A, there are two types of piriformis syndrome- primary and secondary.

Primary piriformis syndrome

Primary piriformis syndrome has an anatomical cause, with variations such as a split piriformis muscle, split sciatic nerve, or an anomalous sciatic nerve path. Among patients with piriformis syndrome, fewer than 15% of cases have primary causes.[3] At present, there are no accepted values for the prevalence of the anomaly and little evidence to support whether or not the anomaly of the sciatic nerve causes piriformis syndrome or other types of sciatica.[9] These findings suggest that piriformis and sciatic anomalies may not be as important to the pathophysiology of piriformis syndrome as previously thought.[9]

Secondary piriformis syndrome

Secondary piriformis syndrome occurs as a result of a precipitating cause, including macrotrauma, microtrauma, ischemic mass effect, and local ischemia.

Piriformis syndrome is most often (50% of the cases) caused by macrotrauma to the buttocks, leading to inflammation of soft tissue, muscle spasms, or both, with resulting nerve compression. Muscle spasms of the PM are most often caused by direct trauma, post-surgical injury, lumbar and sacroiliac joint pathologies or overuse.[4][5][6][10][2][3]PS may also be caused by shortening of the muscles due to altered biomechanics of the lower limb, low back and pelvic regions [7]. This can result in compression or irritation of the sciatic nerve. [4][6][10]

When there is a dysfunction of the piriformis muscle, it can cause various signs and symptoms such as pain in the sciatic nerve distribution, including the gluteal area, posterior thigh, posterior leg and lateral aspect of the foot.[5]Microtrauma may result from overuse of the piriformis muscle, such as in long-distance walking or running or by direct compression. An example of this kind of direct compression is known as “wallet neuritis”, which is a repetitive trauma caused by sitting on hard surfaces.[3]

Other causative factors are anatomic variations of the divisions of the sciatic nerve, anatomic variations or hypertrophy of piriformis muscle, repetitive trauma, sacro-iliac arthritis and total hip replacement.[5][6][12][2] A Morton's Toe can also predispose the patient to developing piriformis syndrome. A fraction of the population is at high risk, particularly skiers, truck drivers, tennis players and long-distance bikers.[5]

Tonley JC[4] had another view about the cause of PS. He said: ”The piriformis muscle may be functioning in an elongated position or subjected to high eccentric loads during functional activities secondary to weak agonist muscles. For example, if the hip excessively adducts and internally rotates during weight-bearing tasks, due to weakness of the gluteal maximus and / or the gluteus medius, a greater eccentric load may be shifted to the piriformis muscle. Perpetual loading of the piriformis muscle through overlengthening and eccentric demand may result in sciatic nerve compression or irritation”.[4]

Characteristics/Clinical Presentation

Patients with piriformis syndrome have many symptoms that typically consist of persistent and radiating low back pain, (chronic) buttock pain, numbness, paraesthesia, difficulty with walking and other functional activities such as pain with sitting, squatting, standing, with bowel movements and dyspareunia in women.[4][5][1][12][3][13][14].

They can also have pressure pain on the buttock on the same side as the piriformis lesion and point tenderness over the sciatic notch in almost all instances.[13]]

Swelling in the legs and disturbances of sexual functions have also been observed in patients with PS.[13]

The buttock pain can radiate into the hip, the posterior aspect of the thigh and the proximal portion of the lower leg.[4]

There may be an aggravation of pain with activity, prolonged sitting or walking, squatting, hip adduction and internal rotation and maneuvers that increase the tension of the piriformis muscle.[4][5][1][12]

Depending on the patient, the pain can lessens when lying down, bending the knee or when walking. However, some patients cannot tolerate the pain in any position and can only find relief when they’re walking.[14][13]

Piriformis syndrome is not characterized by neurological deficits typical for a radicular syndrome, such as declined deep tendon reflexes and myotomal weakness. The patient may present with a limp when walking or with their leg in a shortened and externally rotated position while supine[1][13]. This external rotation while supine can be a positive piriformis sign, also called a splayfoot. It can be the result of a contracted piriformis muscle.[6][3]

Three speciﬁc conditions may contribute to PS:

Myofascial referred pain from trigger points in the PM

Adjacent muscles, nerve and vascular entrapment by the PM at the greater sciatic foramen

Pathology

Primary piriformis syndrome has an anatomic cause, such as a split piriformis muscle, split sciatic nerve, or an anomalous sciatic nerve path.

Secondary piriformis syndrome occurs as a result of a precipitating cause, including macrotrauma, microtrauma, ischemic mass effect, and local ischemia.

Among patients with piriformis syndrome, fewer than 15% of cases have primary causes. Piriformis syndrome is most often caused by macrotrauma to the buttocks, leading to inflammation of soft tissue, muscle spasm, or both, with resulting nerve compression. Microtrauma may result from overuse of the piriformis muscle, such as in long-distance walking or running or by direct compression. An example of this kind of direct compression is “wallet neuritis” (ie, repetitive trauma from sitting on hard surfaces).

Investigations

Radiographic studies have limited application to the diagnosis of piriformis syndrome. Although standard antero-posterior radiographs of the pelvis and hips, lateral views of the hips and either CT or MRI of the lumbar spine are recommended to rule out the possibility that the symptoms experienced by the patients originate from the spine or the hip joint.[11]

Electromyography (EMG) may be also beneficial in differentiating piriformis syndrome from other possible disorders, such as intervertebral disc herniation. Interspinal nerve impingement will cause EMG abnormalities of muscles proximal to the piriformis muscle. In patients with piriformis syndrome however, EMG results will be normal for muscles proximal to the piriformis muscle and abnormal for muscles distal to it.

Electromyography examinations that incorporate active maneuvers, such as the FAIR test, may have a greater specificity and sensitivity than other available tests for the diagnosis of piriformis syndrome[3]

Outcome Measures

Examination

A complete neurological history and physical assessment of the patient is essential for an accurate diagnosis. The physical assessment should include the following points:

an osteopathic structural examination with special attention to the lumbar spine, pelvis and sacrum, as well as any leg length discrepancies

diagnostic tests

deep-tendon reflex testing, strength and sensory testing

Diagnostic tests

Palpation

The patient reports sensitivity during palpation at the greater sciatic notch, in the region of sacroiliac joint or over the piriformis muscle belly. It is possible to detect the spasm of the PM by careful, deep palpation.[6][1][12]

With deep digital palpation in the gluteal and retro-trochanteric area, there may be tenderness and pain with an exacerbation of tightness and leg numbness.[16]

Pace sign

Pace’s sign consists of pain and weakness by resisted abduction and external rotation of the hip in a sitting position. A positive test is occurs in 46.5% of the patients with piriformis syndrome.[5][1][3][11]

Freiberg sign

Involves pain and weakness on passive forced internal rotation of the hip in the supine position. The pain is thought to be a result of passive stretching of the piriformis muscle and pressure placed on the sciatic nerve at the sacrospinous ligament. Positive in 56,2% of the patients.[11]

Beatty’s maneuver

An active test that involves elevation of the flexed leg on the painful side, while the patient is lying on the asymptomatic side. The abduction causes deep buttock pain in patients with PS, but back and leg pain in patients with lumbar disc disease.[11]

The Hughes test

External isometric rotation of the affected lower extremity following maximal internal rotation may also be positive in PS patients.[11]

Hip Adbuction Test

The patient lies on the side with lower leg flexed to provide support and the upper leg straight, in line with the trunk. The practitioner stands in front of the patient at the level of the feet and observes (no hands on) as the patient is asked to abduct the leg slowly.

Injections of local anaesthetics, steroids, and botulinum toxin into the PM muscle can serve both diagnostic and therapeutic purposes. The practitioner should be familiar with variations in the anatomy and the limitations of landmark-based techniques. An ultrasound guided injection technique has recently been utilized. This technique has been shown to have both diagnostic and therapeutic value in the treatment of PS.[11]

Piriformis syndrome often becomes chronic and pharmacological treatment is recommended for a short time period.[16]

Surgical management

Surgical interventions should be considered only when nonsurgical treatment has failed and the symptoms are becoming intractable and disabling. Classic indications for surgical treatment include abscess, neoplasms, hematoma, and painful vascular compression of the sciatic nerve caused by gluteal varicosities.[11]

Surgical release with tenotomy of the piriformis tendon to relieve the nerve from the pressure of the tense muscle has resulted in immediate pain relief, as reported by several authors.

Sometimes, the obturator internus muscle should be considered as a possible cause of sciatic pain. However, the diagnosis of the obturator internus syndrome can only be made by ruling out other possible causes of sciatic pain, which is similar to the manner in which piriformis syndrome is diagnosed.[16] Surgical release of the internal obturator muscle can result in both a short- and long-term reduction in pain in patients with retro-trochanteric pain syndrome and should be considered if conservative treatment fails.

Physical Therapy Management

Although there is a paucity of recently published controlled trials in which critically examine the effectiveness of the noninvasive management modalities[11], a number of methods exists for the treatment of ‘Piriformis Syndrome’.

According to Tonley et al., the most commonly reported physical therapy interventions include ultrasound, soft tissue mobilization, piriformis stretching, hot packs or cold spray and various lumbar spine treatments (evidence level 2A). In addition, its case report Tonley et al. describes an alternative treatment approach for piriformis syndrome. The intervention focused on functional exercises Therapy Exercises for the Hipaimed at strengthening the hip extensors, abductors and external rotators, as well as correction of faulty movement patterns (evidence level 4). Despite positive outcomes (level of evidence 4) full resolution of low back pain, cessation of buttock and thigh pain) in this single case report care must be taken in establishing cause and effect based on a single patient. Further investigation is needed[4]

First of all, the patient must be placed in contralateral decubitus and FAIR position (Flexed Adducted Internally Rotated). Start with an ultrasound treatment: 2.0-2.5 W/cm2, for 10-14 minutes. Apply the ultrasound gel in broad strokes longitudinally along the piriformis muscle from the conjoint tendon to the lateral edge of the greater sciatic foramen.[4][5][15][2][18][3] (level of evidence 2b) Before stretching the piriformis muscle, treat the same location with hot packs or cold spray for 10 minutes. The use of hot and cold before stretching is very useful to decrease pain. [4][5][15][18][3] After that, begin with stretching of the piriformis which can be executed in a variety of ways. Stretch the piriformis muscle by applying manual pressure to the muscle’s inferior border. It is important not to press downward, rather directing pressure tangentially, toward the ipsilateral shoulder. When pressing downward, the sciatic nerve will compress against the tendinous edge of the gemellus superior. However, when applying tangential pressure, the muscle’s grip will weaken on the nerve and relieve the pain of the syndrome.[4][15][18][3]

Another way to stretch this muscle is in the FAIR position. The patient lies in a supine position with the hip flexed, adducted and internally rotated. Then the patient brings his foot of the involved side across and over the knee of the uninvolved leg. We can enhance the stretch, by letting the physical therapist perform a muscle–energy technique. This technique involves the patient abducting his limb against light resistance, which is provided by the therapist for 5-7 seconds, with 5-7 repetitions.[5][6][15][18]

After stretching, continue with myofascial release at the lumbosacral paraspinal muscles and McKenzie exercises. When the patient lies in the FAIR position, the lumbosacral corset can be used.[15][18][3]

The therapist can also give several tips to avoid an aggravation of the symptoms. This includes:

Avoid sitting for a long period

Stand and walk every 20 minutes

Make frequent stops when driving to stand and stretch

Prevent trauma to the gluteal region

Avoid further offending activities.

Daily stretching is recommended to avoid the recurrence of the piriformis syndrome.[5][6][3]

The patient can also perform several exercises and treatments at home including:

Rolling side to side with flexion and extension of the knees while lying on each side

Rotate side to side while standing with the arms relaxed for 1 minute every few hours

Take a warm bath

Lie flat on the back and raise the hips with your hands and pedal with the legs like you are riding a bicycle

Clinical Bottom Line

Piriformis syndrome (PS) is a painful musculoskeletal condition and is most often caused by macrotrauma to the buttocks, leading to inflammation of soft tissue, muscle spasms, or both, with resulting nerve compression.

Patients with piriformis syndrome have many symptoms that typically consist of persistent and radiating low back pain, (chronic) buttock pain, numbness, paraesthesia, difficulty with walking and other functional activities.

A complete neurological history and physical assessment of the patient is essential for an accurate diagnosis. The physical assessment should include the following points:

osteopathic structural examination with special attention to the lumbar spine, pelvis and sacrum, as well as any leg length discrepancies

diagnostic tests

deep-tendon reflex testing, strength and sensory testing

When diagnosed, patients need to first rest and then adjustments are needed in regards to repetitive overloads placed on the body. NSAIDs and non-opiod pain medications are recommended for a short period but patients need to perform physiotherapy including stretching and direct non-invasive treatment of the retro-trochanteric region. Surgical intervention should be considered only when nonsurgical treatment has failed and the symptoms are becoming intractable and disabling.

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